Shrimp dating zircon
Together with other studies we suggested that the collision of ocean and continent plates may occur at the early Caledonian in this area, forming the eclogite, and the collision of continent and continent plates at the late Caledonian, forming the Qaidamshan granite with the zircon SHRIMP age of 446 Ma.
There is an increasing evidence for the involvement of pre-Neoproterozoic zircons in the Arabian-Nubian Shield, a Neoproterozoic crustal tract that is generally regarded to be juvenile.
The source and significance of these xenocrystic zircons are not clear.
In an effort to better understand this problem, older and younger granitoids from the Egyptian basement complex were analyzed for chemical composition, SHRIMP U-Pb zircon ages, and Sm-Nd isotopic compositions.
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The team examined samples and found zircons dating back three billion years in a piece of the island’s six-million-year-old piece of igneous volcanic rock.
We think that both granite and eclogite may be formed at different stages during tectonic evolution of this area.
The U-Pb SHRIMP dating of zircons revealed the ages of magmatic crystallization as well as the presence of slightly older, presumably inherited zircon grains.
The age determined for the older granodiorite is 652.5 ± 2.6 Ma, whereas the younger granitoids are 595-605 Ma.
8 Ma, which is consistent with previous reported UHP metamorphic ages from eclogite pods and country-rock gneisses.
The Xugou mafic lenses may have formed by partial melting of the enclosing peridotites in the mantle before subduction (Zhang et al., 2003); then these eclogites, together with the host peridotites, were tectonically emplaced into the subduction zone and subjected to UHP metamorphism at 237 ??
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